According to a known technique (see, for example, JP2013-232654A), a circuit board having electronic components mounted thereto is assembled with a heat sink to release heat generated from the electronic components, and a heat conductive material is interposed between the electronic components and the heat sink. According to this technique, the heat conductive material is applied to one of the circuit board and the heat sink, and thereafter the circuit board and the heat sink are assembled together to compress and spread the heat conductive material between the circuit board and the heat sink.
However, according to the technique of JP2013-232654A, it is not possible to visually recognize whether the heat conductive material covers the electronic component after the assembling of the circuit board and the heat sink together. Therefore, according to the prior art technique, the heat conductive material is applied in the sufficient amount to cover the entirety of the subject electronic component before the time of assembling the circuit board and the heat sink together. Thus, a bonding range of the heat conductive material after the assembling is unnecessarily enlarged relative to the subject electronic component. Thereby, the amount of the heat conductive material to be used may be excessively increased.